The results of a study of 1,911 elderly patients suggest that beyond chronologic aging, both sensory impairments may be markers of biologic aging and may also share common risk factors, according to a report in the October issue of the Archives of Ophthalmology.

A strong age-related increase in vision and hearing impairment has highlighted concerns about the effect of these sensory losses among the growing number of older adults, said Paul Mitchell, M.D., Ph.D., of the University of Sydney here, and colleagues. "To our knowledge," they wrote, "no population-based study has described whether there is an association between age-related vision and hearing impairment."

The Australian study involved a re-examination after five years of participants (original mean age 69.8 years) who were part of the 1997-1999 Blue Mountain Eye Study.

Of the participants, 178 (9.3%) participants were visually impaired (visual acuity less than 20/40 in the better eye), while 56 (2.9%) had best-corrected visual impairment (less than 20/40 with glasses or contacts).

Conversely, participants with impaired hearing were 50% more likely to be visually impaired (age- and gender-adjusted OR, 1.5, CI 1.0-2.1). This association was slightly stronger among those with more severe hearing loss with an adjusted OR of 1.6 (CI, 1.1-2.6).

Each individual impairment as well as the combined sensory loss increased markedly with age (P trend <0.001), the researchers reported.

Analysis of the two principal causes of vision impairment, cataracts and age-related macular degeneration, found that both were independently associated with hearing loss.

Participants with any cataract were more likely to have hearing loss, after adjusting for confounders (OR 1.2, CI 1.0-1.5). Those younger than 70 with any form of cataract, were also significantly more likely to have moderate to marked levels of hearing impairment.

Participants with age-related macular degeneration were also more likely to have hearing loss, while, again, the association was stronger in participants younger than age 70, the researchers reported.

In addition, these two impairments were found to have a cumulative effect on functional status, independence, and well-being, significantly affecting both physical and mental domains, Dr. Mitchell's team wrote. Components were assessed using the 36 items on the Short-Form Health Survey (SF-36).

After adjusting for demographic and medical confounders, the researchers found lower scores on SF-36 among participants with both vision and hearing impairments than among those with only one loss (multivariate-adjusted SF-36 mean component scores; P trend = 0.001 and <0.001, respectively).

These findings are consistent with other studies, the investigators wrote. The strong age-related increases in the prevalence of cataract and age-related macular degeneration have been well documented. However, they said, the relationship between these impairments remained, even after adjusting for age.

Still, they said, the results suggest that both losses are likely markers of aging. However, they qualified the age factor, saying that the finding that vision and hearing loss are generally stronger in those younger than 70 years suggests that the impairments are markers of biologic rather than chronologic aging.

In addition to aging, the researchers said, certain common risk factors could predispose older individuals to both conditions. Each condition has been postulated to result from somewhat similar genetic, environmental, and lifestyle factors.

Exposure to oxidative stress, cigarette smoking, and atherosclerosis and its risk factors have been linked respectively to age-related macular degeneration, cataract, and hearing loss. Diabetes is another common risk factor for these impairments, they said. Irrespective of the cause, these two impairments have a cumulative effect on quality of life.

Limitations of the study, the researchers noted, include its cross-sectional design, which made it impossible to establish the nature of the observed association between the two sensory impairments. Other limitations include possible observational bias inherent in the use of a single ophthalmologist to determine the causes of visual impairment.

"Our study confirms some previous findings that there is a significant, modest association between vision and hearing impairments in older persons, after accounting for the effect of age," Dr. Mitchell and his team wrote. Further studies are needed, they said, to determine whether intervention to improve these impairments could delay biologic aging.

Reviewed by
Rubeen K Israni, MD, Fellow, Renal-Electrolyte and Hypertension Division, University of Pennsylvania School of Medicine

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